The present invention relates to a power transmission control device, a power transmitting device, an electronic instrument, a non-contact power transmission system, and the like.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charging a household appliance (e.g., cordless telephone handset), and the like have been proposed.
JP-A-2006-60909 discloses related-art non-contact power transmission technology. According to the technology disclosed in JP-A-2006-60909, a primary-side instrument (power-transmitting-side instrument) monitors the peak value of an induced voltage signal of a primary coil, and compares the peak value with a given threshold voltage to detect the load state of a secondary-side instrument (power-receiving-side instrument) so that a foreign object (e.g., metal) is detected. Specifically, the primary-side instrument determines that a foreign object is electromagnetically coupled to the primary coil instead of the secondary coil when the primary-side instrument has determined that the load state of the secondary-side instrument has become equal to or higher than the normal load rating due to an eddy current loss or the like caused by a foreign object inserted between the primary coil and the secondary coil, for example.
According to the technology disclosed in JP-A-2006-60909, a primary-side detection circuit detects an eddy current loss or the like due to a foreign object. However, it is difficult for the detection circuit to determine whether the power-receiving-side load is a normal load or a pseudo-load due to a foreign object.